The present invention relates to an assembly of a passive-type autofocus module that is incorporated in an autofocus camera.
As is well known, recent autofocus cameras have a passive-type autofocus module which measures a distance to an object by forming its image on a one-dimensional image sensor and processing a resulting image signal.
FIGS. 4(a) and 4(b) show a conventional autofocus module assembly, in which reference numeral 1 represents an autofocus IC; 2, a pair of separator lenses arranged side by side; and 3, a light-shield box. The autofocus IC 1 is formed by sealing an IC chip 1a in a mold package 1b made of a transparent resin. Leads 1c are laterally extended from the mold package 1b.
To assemble the above module, first the lenses 2 are attached to the top surface of the light-shield box 3, which is then mounted on the package 1b at a predetermined position. Then, an ultraviolet-curing-type adhesive 4 applied between the package 1b and each of bifurcate leg portions 3a protruded at the two sides of the bottom surface of the light-shield box 3 is illuminated with ultraviolet light from a position laterally spaced from the light-shield box 3. As a result, the adhesive 4 sets to bond the leg portion 3a to the package 1b. By virtue of the use of the ultraviolet-curing-type adhesive 4, mere illumination by ultraviolet light accelerates the setting reaction to provide a short setting time without necessitating a heat treatment, which might adversely affect the autofocus IC 1.
However, the following problems occur in setting the ultraviolet-curing-type adhesive 4 applied between the light-shield box 3 and the package 1b of the autofocus IC 1 by illuminating it with ultraviolet light.
Since the conventional light-shield box 3 is made of an opaque resin, when ultraviolet light is emitted from light sources provided near the light-shield box 3 (on both sides of a conveyer in an actual production line), part of the light is blocked by the bottom face and the back face of the leg portion 3a and does not reach the adhesive 4, to produce non-set portions, which may cause a bonding defect. To avoid this problem, in the conventional assembling process, an additional light source is provided so as to illuminate the adhesive 4 in a different direction, i.e., toward the back face of the leg portion 3a of the light-shield box 3. However, in an actual production line, it is difficult to do so because a conveyer, various jigs, etc. may act as obstacles. Further, the increase of the number of light sources results in an increase of power consumption.